Various appliances and methods are used for the purpose of vacuum packaging and sealing plastic bags and containers to protect perishables, such as foodstuffs, and other products against oxidation. Conventional commercial devices and some consumer appliances are generally expensive to manufacture, complex in construction and/or cumbersome to operate. One conventional type of vacuum sealing system, primarily used for commercial packaging purposes, includes a vacuum chamber in which the entire packaged product is placed, along with heat sealers and attendant components of the system.
Another type of conventional vacuum sealing system uses a vacuum nozzle that is inserted within a plastic bag for evacuation purposes. Although adaptable for low-volume home use, this type of system is cumbersome to use and normally requires a liquid separator or filter to prevent liquids or powders, retained within the bag, from being drawn into a vacuum pump connected to the nozzle. Further, the heat sealer employed therein must be closely calibrated and synchronized with the positioning and withdrawal of the vacuum nozzle from the bag.
Still another known vacuum sealing system places a portion of a bag, containing a product to be packaged, in a first vacuum chamber and extends an open end or neck of the bag into a second vacuum chamber. The first vacuum chamber is then evacuated to expand the neck of the bag to isolate the chambers from each other. Then a vacuum is drawn in the second vacuum chamber to evacuate the bag. Thus, isolation of the two chambers from each other, during evacuation of the second vacuum chamber, is dependent on the physical properties composing the neck of the bag (which is intended to form a static seal between the two chambers) and very close synchronization and calibration of the evacuation and sealing procedures and controls therefor. A vacuum sealing system of this type is disclosed in U.S. Pat. No. 3,928,938, for example.
U.S. Pat. No. 2,778,171 discloses another vacuum sealing system, which is not believed to have been commercialized. In particular, the open end of a plastic bag is placed between a pair of jaws or between a lower jaw and a flexible sheet to evacuate the bag that is then heat-sealed. An inner surface of the bag has protuberances that make point contact with an opposite surface of the bag to define air exhaust passages during evacuation of the bag. More recent successfully marketed appliances are described in U.S. Pat. No. 4,941,310, the complete contents of which is incorporated herein by reference.
During operation of the home vacuum packaging appliance, the user must be provided a mechanism for maintaining the integrity of the vacuum circuit. Typically this is accomplished by requiring the user to manually depress on a lid of the home vacuum packaging appliance and maintain pressure while the bag or container is evacuated. What is needed is a simpler and more reliable mechanism for maintaining the integrity of the vacuum circuit during operation of the vacuum packaging appliance.